diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
index dbb9a475..2245da5b 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
@@ -442,11 +442,12 @@ public sealed class S7Driver
? parsed
: S7AddressParser.Parse(tag.Address);
- // Array path: a tag with a declared count > 1 reads a CONTIGUOUS block of
+ // Array path: a tag with a declared count >= 1 reads a CONTIGUOUS block of
// count × element-bytes in a SINGLE round-trip (Plc.ReadBytesAsync), then decodes each
// element from its big-endian slice into an element-typed CLR array. The scalar path
- // (count null / <= 1) is left byte-for-byte unchanged below.
- if (tag.ArrayCount is > 1)
+ // (count null) is left byte-for-byte unchanged below. A count of 1 IS a valid 1-element
+ // array (the foundation materialises a [1] OPC UA array node when isArray:true).
+ if (tag.ArrayCount is >= 1)
return await ReadArrayAsync(plc, tag, addr, ct).ConfigureAwait(false);
// S7.Net's string-based ReadAsync returns object where the boxed .NET type depends on
@@ -793,10 +794,10 @@ public sealed class S7Driver
var folder = builder.Folder("S7", "S7");
foreach (var t in _options.Tags)
{
- // A tag carrying an array count (> 1) surfaces as a 1-D OPC UA array node; a missing
- // count or a count of 1 stays scalar (count == 1 array adds no information over a
- // scalar and would force every read down the slower block path).
- var isArray = t.ArrayCount is > 1;
+ // A tag carrying a non-null array count (>= 1) surfaces as a 1-D OPC UA array node.
+ // A null count stays scalar. A count of 1 IS a valid 1-element array: the foundation
+ // materialises a [1] OPC UA array node when isArray:true, so the driver must agree.
+ var isArray = t.ArrayCount is >= 1;
folder.Variable(t.Name, t.Name, new DriverAttributeInfo(
FullName: t.Name,
DriverDataType: MapDataType(t.DataType),
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7ArrayReadTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7ArrayReadTests.cs
index 92167a0c..90575033 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7ArrayReadTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests/S7ArrayReadTests.cs
@@ -216,9 +216,11 @@ public sealed class S7ArrayReadTests
arr.ArrayDim.ShouldBe(8u);
}
- /// Verifies a tag with ArrayCount of 1 is treated as a scalar (no array node).
+ /// Verifies a tag with ArrayCount of 1 is treated as a 1-element array (not scalar).
+ /// The foundation materialises a [1] OPC UA array node when IsArray=true, so the driver must
+ /// honour isArray:true + arrayLength:1 — a 1-element array IS a valid array.
[Fact]
- public async Task DiscoverAsync_count_of_one_is_scalar()
+ public async Task DiscoverAsync_count_of_one_is_array()
{
var opts = new S7DriverOptions
{
@@ -231,8 +233,40 @@ public sealed class S7ArrayReadTests
await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken);
var one = builder.Variables.Single().Attr;
- one.IsArray.ShouldBeFalse("count<=1 is scalar");
- one.ArrayDim.ShouldBeNull();
+ one.IsArray.ShouldBeTrue("ArrayCount=1 is a 1-element array, not scalar");
+ one.ArrayDim.ShouldBe(1u);
+ }
+
+ /// Verifies that a tag with a null ArrayCount (scalar) is still discovered as scalar.
+ [Fact]
+ public async Task DiscoverAsync_null_ArrayCount_is_scalar()
+ {
+ var opts = new S7DriverOptions
+ {
+ Host = "192.0.2.1",
+ Tags = [new("Scalar", "DB1.DBW0", S7DataType.Int16, ArrayCount: null)],
+ };
+ using var drv = new S7Driver(opts, "s7-arr-null");
+
+ var builder = new RecordingBuilder();
+ await drv.DiscoverAsync(builder, TestContext.Current.CancellationToken);
+
+ var scalar = builder.Variables.Single().Attr;
+ scalar.IsArray.ShouldBeFalse("null ArrayCount is scalar");
+ scalar.ArrayDim.ShouldBeNull();
+ }
+
+ /// Verifies a read of an isArray:true arrayLength:1 equipment tag returns a 1-element typed array.
+ [Fact]
+ public void DecodeArrayBlock_count_of_one_returns_single_element_array()
+ {
+ // A 1-element Int16 array: one big-endian word.
+ var block = BeWords(0x0064); // 100
+ var result = S7Driver.DecodeArrayBlock(ArrTag(S7DataType.Int16, 1), Addr(S7Size.Word), block);
+
+ var arr = result.ShouldBeOfType();
+ arr.Length.ShouldBe(1);
+ arr[0].ShouldBe((short)100);
}
// ── Equipment-tag resolver threads arrayLength → ArrayCount ───────────────────────────